Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$182.62	9.407%	$199.7991	$199.80	$199.80	$199.80
Purchase #2	$46.88	7.138%	$50.2263	$50.23	$50.25	$50.20
Purchase #3	$68.72	13.860%	$78.2446	$78.24	$78.25	$78.20
Purchase #4	$65.34	3.284%	$67.4858	$67.49	$67.50	$67.50
Purchase #5	$100.47	8.783%	$109.2943	$109.29	$109.30	$109.30
Purchase #6	$138.89	12.632%	$156.4346	$156.43	$156.45	$156.40
Purchase #7	$119.96	10.398%	$132.4334	$132.43	$132.45	$132.40
7 purchase totals =	$722.88		$793.9181	$793.91	$794.00	$793.80